This application relates to fabrication of fiber probes by chemical etching.
Tapered fiber probes may be formed by shaping one end of an optical fiber into a cone or tapered section. The end tip of the cone or tapered section may be used as a small optical aperture for coupling light either out of the fiber or into the fiber. In particular, the fiber tip may be used as an optical probe in a near-field configuration, where light is coupled over a spacing less than one wavelength of the coupled light, for various optical imaging or sensing applications. For example, such a fiber tip may be used in a near-field scanning optical microscope to achieve a spatial resolution higher than what is permissible by the far-field diffraction limit.
The quality of the fiber probes has been shown to have significant impact on the performance of a near-field system using a fiber probe. Various fabrication techniques have been developed to achieve a small, sharp fiber probe with a smooth side surface in the tapered section. In particular, chemical wet-etching techniques have been used to etch a bare fiber with a suitable etching liquid to fabricate the fiber probe. The etching liquid may be a solution with various active chemicals such as hydrofluoride acid (HF) or a mixture of an oxidizing acid and hydrogen peroxide. For example, U.S. Pat. No. 4,469,554 to Turner et al. and U.S. Pat. No. 5,985,166 to Unger et al. describe wet etching of a bare fiber at the meniscus interface of the etching liquid with the side of the bare fiber. Lambelet et al. also disclosed a fabrication method that uses the fiber jacket to better control the wet etching at the meniscus interface in “CHEMICALLY ETCHED FIBER TIPS FOR NEAR-FIELD OPTICAL MICROSCOPY: A PROCESS FOR SMOOTHER TIPS,” Applied Optics, Vol. 37, pages 7289-7292 (1998).